Synchronous motor clock system



1934- G. F. HARTER SYNCHRONOUS MOT OR CLOCK SYSTEM Filed July 21, 1932 2 Sheets-Sheet 1 Wi l Ge 2 e Fffarter; z /wziiflwv y if Ays.

NOV. 6, 1934. HARTER 1,979,326

SYNCHRONOUS MOTOR CLOCK SYSTEM Filed July 21, 1932 2 SheetsSheet 2 @IKQ IWI W //0 M AC.

Jwvezzfm; 6'60?" 61 715124 Atty Patented Nov. 6, 1934 v 1,979,326 SYNCHRONOUS MOTOR CLOCK SYSTEM George F. Barter, Springfield, Mesa, assignor to The Standard Electric Time Company, Springfield, Mass., a. corporation of Connecticut Application July 21, 1932, Serial No. 623,724

10 Claims.

This invention relates to electric clock systems, especially of the type in which the secondary clocks (time recorders, time stamps, etc.) are driven step by step by impulses transmitted at regular intervals such as once per minute, and

more particularly to means for keeping the clocks running during periods of current interruption. The principal objects of the invention are to provide a system having emergency apparatus which functions automatically during current interruption, which consumes little energy in operation, which permits periodic synchronization of the clocks during both normal and emergency operation, which is simple and inexpensive in construction, which is reliable and durable in use, and generally to improve systems of the type referred to.

For the purpose of illustration typical concrete embodiments are shown diagrammatically in the accompanying drawings in which,

Fig. 1 is a simple embodiment of the invention showing the parts in normal operating condition;

Fig. 2 is a similar view showing the parts in emergency position; and

Figs. 3 and 4 are similar diagrams of other embodiments of the invention showing the parts in normal operating position.

The particular embodiment illustrated in Figs. 1 and 2 comprises a source of alternating current connected to the circuit 1, a rectifier 2 connected to the circuit 1 through transformer 3, secondary clocks S, an impulse switch 4 for transmitting impulses of current from the rectifier 2 to the secondary clocks over the circuits 5, 6, 7 and 8, and

' a synchronous motor M for actuating the switch 4 through the contacter 13, the motor M normally receiving current from the circuit 1 over the con ductors 14 and 1'7. In addition to the foregoing, which comprises the normally operating portions of the system, the apparatus also comprises a twoway switch consisting of three contacts 31, 32 and 33 movable between the upper normal position shown in Fig. 1 and the lower emergency position shown in Fig. 2. The contact 31 engages a. contact 34 when in the upper position and a contact 35 when in the lower position; the contact 33 engages a contact 36 when in the upper position and a contact 37 when in the lower position; and the contact 32 engages only one contact, namely, contact 38 when in the lower position. The contacts 31, 32 and 33 are normally held in upper position by a solenoid 39 connected to the circuit 1 over the conductors 40. The contacts 3'? and 38 are connected together and thence over circuit 41 to the battery 42, the upper end of which is connected to the conductor 5. The contacts 34 and 36 are connected to the conductors 1'7 and 8 respectively above referred to. The contact 35 is connected over conductor 43 to one end of the secondary 44 of a transformer, the other end of a secondary being connected to the motor M over the conductor 45. The contact 32 is connected over conductor 46 to the vibrator 47 of apparatus for producing alternating current from direct current of the type commonly called a pole-changer. The particular apparatus shown in the drawings differs from the ordinary pole changer in that it is provided with a transformer of the split or double-wound primary type. The opposite ends of the primary 51 are connected to the two contacts 52 and 53 which are alternately engaged by the vibratory element 47 when it swings back and forth. A condenser 54 is connected across the end of the primaries and an intermediate point of the primary is connected to the conductor 5 over a conductor 55. Associated with the vibratory element 47 is a third contact point 56 which engages the element each time it swings to the right, also engaging the element when the latter stands in neutral position as shown in Fig. 1. This contact is also connected to the conductor 5 over a conductor 57 which includes a resistance 58 and an electromagnet 59 for swinging the vibratory element 47.

With the parts in the normal position, as shown in Fig. 1, that is, with the two-way switch in the upper position, the motor M is supplied with alternating current from the circuit 1 over the conductors 14 and 17 through switch contact 34. With the motor armature and the circuitcloser 13 thus driven at a constant speed (which is ordinarily one revolution per minute) regular driving impulses are transmitted to the secondary clocks from the rectifier 2 over the circuit comprising conductors 5, 6, 7 and 8 and switches 4 and 36. Upon failure of the alternating current source connected to the circuit 1 the electromagnet 39 is deenergized and the two-way switch moves to the lower position shown in Fig. 2. This substitutes the battery 42 for the rectifier 2 so that the impulses are then transmitted to the secondary clocks over the circuits 5, 6, 7 and 41, through switch contacts 4 and 33-37. During this emergency operation the motor' M is supplied. with alternating current of the same frequency as that normally supplied from circuit 1, the emergency current being supplied from the secondary 44 through conductors 43 and 45 and the switch contacts 31 and 35. This current is supplied in the following manner: When the twosure of switch 32-38 closes the following vcircuits: conductor 41, battery 42, conductors 5 and '57, electromagnet 59, contact .56, conductor 46,

back to switch 32-38. This energizes the magnet 59 causing the vibratory element 47 to swingtery 42, conductors 5 and .55 and the left-hand end of the primary; and when the element swings to the right into contact with 53 current flows through the primary of the transformer in the opposite direction over the same circuit except in that contact 53 and the right-hand end of the primary are substituted for the contact 52 and the left-hand end of the primary. By suitably regulating the physical and electrical characteris'tics of this apparatus it may be caused to deliver to the motor M alternating current having a frequency which is constant and the same as that normally received from the circuit 1. When normal current is restored to circuit 1 the electromagnet 39 is immediately energized to restore the two-way switch to its normal upper position, whereupon the rectifier 2 is resubstituted for the battery 42 in the clock circuit, the motor M continues to run in response to current from circuit 1 and the vibrator 47 comes to rest in the position shown in Fig. 1 owing to the opening of switch contacts 32-38.

To a large extent the system of Fig. 3 is like that of Figs. 1 and 2 and inasmuch as the corresponding parts have been correspondingly designated the description thereof need not be repeated. In addition to the parts already described the system of Fig. 3 comprises a second switch 60 which is periodically closed by the synchronous motor M to transmit synchronizing impulses to the secondary clocks over the conductors 61, 5, 7 and either 8 or 41 depending upon whether the switch 33 is in upper or lower position. In this case the secondary clocks each have two electromagnets D and R. The magnets D are the driving magnets, corresponding to the single magnets in the secondary clocks of the embodiment shown in Figs. 1 and 2, and are therefore connected between the same conductors 5 and 6. The additional electromagnets R serve to synchronize the clocks at relatively infrequent intervals such as once per hour. These synchronizing magnets may function in various ways as,

for example, in the manner disclosed in copending application Serial No. 580,625 filed December 12, 1931. When arranged to synchronize the secondary clocks once per hour the switch 60 is preferably timed to transmit a single impulse to the magnets R between the 59th and 60th minute impulses transmitted by the switch 4. In normal operation the magnets R receive current from rectifier 2 over the circuit; conductor 5, rectifier 2, conductor 8, switch 36-33, conductor 7, switch 60 and conductor 61. When the normal source of alternating current fails and the switch contact 33 is thereby transferred from contact 36 to contact 37 the control of the synchronizing electromagnets is transferred to the battery 42 so that when the switch 60 closes the synchronizing magnet receives an impulse over the following circuit: conductor 5, battery 42, conductor 41,

1,979,826 .way switch moves to the lower position the closwitch 37-33, conductor 7, switch 60 and conductor 61. Thus, during failure of the normal supply of alternating current, the secondary clocks not only continue to be driven at approximately their normal rate but they also continue to be synchronized at the same regular intervals.

Fig. 3 also illustrates a preferred arrangement to give a signal when the main source of power .fails. In this arrangement a bell 72 is connected to conductor 5-thr0ugh conductor 71 and to conductorfi'through a conductor and a switch 31-35. As shown in Fig. 3 this switch is actuated by an electromagnet 39' connected across main line 1 but it will of course be understood that this switch may be controlled by the same electromagnet 39 that controls the switches 31-35, 32-38 and 33-37. When the main current fails the bell is connected in parallel with the regular impulse magnets of the secondary clocks and the bell, which is preferably of the single stroke type, is actuated once per minute.

Thesystem illustrated in Fig. 4 is in part like the preceding figure, corresponding parts being correspondingly designated. This system differs from that shown in Fig. 3 in that the secondary clocks are constructed differently and in that different means are provided for synchronizing the secondary clocks at periodic intervals such as once per hour. In Fig. 4 the secondary clocks each comprises a driving magnet D corresponding to D of Fig. 3 together with a branch circuit having a one-way valve or rectifier V in one branch and a switch 50 in the other branch which automatically opens that branch at regular intervals by means of a rotating actuator 48 driven by the magnet D. The driving impulses are transmitted to the secondary clocks in such manner that they are obstructed by the valve V and must therefore go through the switch 50. Consequently when the clock advances to the point where the switch 50 is opened by rotor 48 the clock becomes unresponsive to the driving impulses, then responding only to a synchronizing impulse transmittedthrough the valve V in the reverse direction. In this case the master clock driven by the synchronous motor M comprises a cam element or controller 10 which may be mounted on the minute arbor to rotate at the rate of one revolution per minute. The controller is provided with a cam projection 11 and a recess 12 which are located at positions approximating the 59th and 60th minute positions of the minute hand, during which period the secondary clocks are brought into synchronism with the master clock. A single-pole, doublethrow switch 15 carries a lug 16 and is arranged to engage the controller and is normally held in neutral position between contacts 18 and 19. When the lug 16 engages the cam projection 11 the switch 15 engages the'contact 18, and when the lug drops into the recess 12 the switch is moved (by a spring e. g.) to engage contact 19. The design of the parts is such that for approximately 59 minutes of each hour the switch 15 is held in neutral position, and for a period of from 20 to 40 seconds between the 59th and 60th minute the switch 15 engages the contact 18, and

and 30 being timed to close more frequently, preferably once per second. The relay 26 is operated by the controller 10 which closes the circuit through contact 19 to energize relay 26, and

the relay 21 is under the conjoint control of contact maker 29 and relay 26. As shown in Fig. 4 each of the relay magnets are connected to the conductor 5 which leads to a point intermediate the rectifier 2 and the battery 42.

The operation of the system is as follows: With the switch 15 in neutral position, the circuits through relays 21 and 26 remain normally open and the circuit through the relay 22 is normally closed at 28. The momentary closing of contact 29 energizes the relay 22 which closes switch 24 and thus effects the transmission of driving impulses of normal polarity over the lines N-N which, as shown in Fig. 4, involves the connection of the conductor N to the positive side of either the rectifier 2 or the battery 42, depending upon the position of the two-way switch. Between the 59th and 60th minute impulses, the cam projection 11 moves switch 15 into engagement with contact 18 and thus closes the circuit from rectifier 2 (or battery 42) through contacts 18 and 19 and relays 22 and effects the transmission of a series of rapid impulses of normal polarity for a period of about 20 to seconds. Just before the th minute impulse the lug 16 drops into recess 12 thereby moving switch 15 from contact 18 to contact 19, thus closing the circuit from the source of current through relay 26. The energization of relay 26 moves the switch 28 to its upper position to close the circuit through relay 21. The relay 26 remains energized for a short interval during which the 60- minute impulse is transmitted by the closing of contact 29 which energizes the relay 21, closing switch 23 and thus efiecting the transmission of 'the 60-minute impulse of opposite or reverse polarity, it being noted that the connections from lines NN' to switch 23 are reversed with respect to the corresponding connection to switch 24. After the transmission of the 60th minute impulse the lug 16 is moved out of recess 12 and the switch 15 is restored to neutral position whereupon relays 26 and 21 become deenergized and switches 28 and 23 return to their normal position as shown in Fig. 4.

Each of the secondary clocks is advanced each minute in response to driving impulses of normal polarity. If for any reason any of the secondary clocks become fast, when they reach the 59th minute, as indicated by their minute hands, the contacts so are opened by cams i8 and they remain unresponsive to further impulses of normal polarity. All clocks that are on time are automatically stopped on the 59th minute in the same manner and will likewise remain unresponsive to further impulses of normal polarity. Should any of the secondary clocks be slow at the 59th minute, as indicated by the hands of the master clock, they will be advanced by the rapid impulses until they are brought into synchronism with the master clock whereupon they will be automatically stopped in the manner previously described; All secondary clocks are thus brought into synchronism with the master clock one minute before the hour. On the 60th minute or even hour, the 60th minute impulse of reverse polarity is transmitted to magnets D (passing through the one-way valves) to advance all clocks to the hour position. In this position the contacts 50 are closed and the operation of the clocks is thus restored to the driving impulses of normal polarity.

In locations where no commercial alternating current is available the circuit 1 may be supplied with alternating current through an inverter from a direct current source. Furthermore, the aforesaid vibratory type 01 means for producing constant frequency alternating current from direct current may of course be replaced by other suitable means for the purpose, as for example, the Thyratron inverter, preferably with crystal control for maintaining constant and accurate frequency.

While the particular embodiment chosen for the purpose of illustration involves the transmission of driving impulses once per minute and synchronization once per hour it will of course be understood that these are only preferred examples and other periods may be employed.

I claim:

1. An electric clock system comprising secondary clocks, main and auxiliary sources of current for normal and emergency operation of the secondary clocks, means for regularly driving t e clocks from either source, means for periodically synchronizing the clocks from either source, and means responsive to the main source of current for automatically rendering both of said means responsive to the auxiliary source when the main source fails.

2. An electric clock system comprising secondary clocks of the impulse type, main and auxiliary sources of current respectively for normal and emergency operation of the clocks, means responsive to either of said sources for transmitting driving impulses at frequent intervals, means responsive to either of said sources for transmitting synchronizing impulses at infrequent intervals, and means responsive to the main source of current for automatically rendering both of said transmitting means responsive to the auxiliary source when the main source falls.

3. An electric clock system comprising secondary clocks, main alternating current and auxiliary battery sources of current respectively for normal and emergency operation of the secondary clocks, means for regularly driving the clocks from either source, means for periodically synchronizing the clocks from either source, and means responsive to the main source of current for automatically rendering both of said means responsive to the auxiliary source when the main source fails.

a. An electric clock system comprising secondary clocks of the impulse type, main and auxiliary sources of current for normal and emergency operation or" the clocks, means for transmitting driving impulses from either of said sources at frequent intervals, means for transmitting synchronizing impulses from either of said sources at infrequent intervals, and means responsive to the main source of current for automatically rendering both of said transmitting means responsive to the auxiliary source when the main source fails.

5. An electric clock system comprising secondary clocks of the impulse type, main and auxiliary sources of current for normal and emergency operation of the clocks, means for transmitting from either source driving impulses at frequent intervals and synchronizing impulses at infrequent intervals, said means including a synchronous motor driven by energy from the main source during normal operation and from the auxiliary source during emergency operation, and means for substituting the auxiliary source when the main source fails.

6. An electric clock system comprising secondary clocks of the impulse type, a source of alternating current for normal operation, a source of direct current for emergency operation, means for transmitting from either source driving impulses at frequent intervals and synchronous impulses at infrequent intervals, said means including a synchronous motor driven by energy from the alternating source during normal operation and from the direct source during emergency operation, means to convert the direct current into alternating current, and automatic switching means for substituting the direct source for the alternating source when the latter fails.

7. An electric clock system comprising secondary clocks of the impulse type, means for transmitting impulses to the clocks including an impulse switch and a synchronous motor for driving the switch, a source of alternating current for normally driving said motor, a source of direct current, and means for supplying to said motor alternating current produced by energy derived from said direct current source.

8. An electric clock system comprising secondary clocks of the impulse type, means for transmitting impulses to the clocks including an impulse switch and a synchronous motor for driving the switch, a source of alternating current for normally driving said motor, and means operative upon failure of said source for supplying to the motor alternating current of approximately the same frequency, said last means comprising a constant frequency interrupter and a transformer having its secondary connected to the motor and its primary connected to a source of direct current through said constant frequency interrupter.

9. An electric clock system comprising second ary clocks of the impulse type,,means including a switch for transmitting impulses to the clocks, a synchronous motor for driving said switch, a bat! tery, a source of alternating current for normally driving said motor, a rectifier connected to said source, a constant-frequency self-acting device, a transformer having its primary connected to said battery through said constant-frequency selfacting device for producing alternating current, means for connecting said motor either to said source or to the secondary of said transformer, and means to connect said switch in series either with said rectifier or with said battery.

10. An electric clock system comprising secondary clocks of the impulse type, means including a switch for transmitting impulses to the clocks, a synchronous motor for driving said switch, a battery, a source of alternating current for normally driving said motor, a rectifier connected to said source, a constant-frequency self-acting device, a transformer having its primary connected to said battery through said constant-frequency self-acting device for producing alternating current, twoway switching means which in one position connects said motor to said source and connects said switch in series with said rectifier and in the other position connects said motor to the secondary of said transformer and connects said switch to said battery, and means for automatically shifting said switching means from the first positionto the second position when said source fails and back again when the source is restored.

GEORGE F. HARTER. 

